The Israeli Prime Minister Benjamin Netanyahu blamed Iran last night for a bomb attack which killed at least seven people and wounded 32 when a bus carrying mainly young Israeli tourists blew up in a Bulgarian Black Sea resort.

The Israeli Prime Minister Benjamin Netanyahu blamed Iran last night for a bomb attack which killed at least seven people and wounded 32 when a bus carrying mainly young Israeli tourists blew up in a Bulgarian Black Sea resort.

As unconfirmed Israeli media reports said that seven had been killed. The airport at Burgas, a popular destination for Israeli holidaymakers, was closed down for civilian flights after the blast. It was not immediately clear whether it had been caused by a suicide bomber or a remotely detonated explosive device.

Most of the passengers aboard the bus were thought to be among around 150 Israelis who had arrived on a flight from Tel Aviv which had landed at the resort's airport at about 4.45pm. The explosion was said by the Israeli Foreign Ministry to have happened around 40 minutes later as the bus –one of three or four conveying the Israeli tourists – was preparing to leave the airport.

One eye witness, Gal Malka who was slightly injured in the explosion, told Israel's Channel 2 TV that she saw someone board the bus before it happened. "We were at the entrance of the bus and in a few seconds we heard a huge boom," she said. The Bulgarian news agency Focus reported that an 11-year-old Israeli girl was among the wounded as well as two pregnant women.

Pictures shown on Israeli and Bulgarian ?television showed smoke billowing out of a car park at the airport, and several buses and cars appeared to be on fire near the shell of the targeted bus, which was to have taken the tourists to their hotel.

Another witness, Shosh Eyler, who was on one of the buses that escaped the explosion, told the Israeli news service Ynet that it took place seconds after the groups boarded the buses. "The bus next to ours just exploded. There was smoke everywhere and people were running hysterically. We got off the bus and local security officers got everyone into the terminal immediately."

Mr Netanyahu said "all the signs point to Iran" and the attack followed others – carried out or attempted – in India, Georgia, Thailand, Kenya and Cyprus, where the authorities said this week they had foiled a plot to target Israeli tourists by the Shia Lebanese guerilla group Hezbollah.

Israel regards Hezbollah's operations outside Lebanon as executed on behalf of Iran. The Prime Minister added: "This is an Iranian terror attack that is spreading across the world," he said. "Israel will react strongly to Iran's terror."

Bulgaria's popularity with Israeli tourists is thought to have further increased as a result of the breakdown in relations between its neighbour Turkey, previously favoured destination for holidaymakers from Israel.

The attacks came amid heightening tensions between Israel and its Western allies on the one hand and Iran on the other over Tehran's nuclear programme, and after persistent Iranian accusations that Israel and the US has been behind a spate of assassinations of its nuclear scientists.

Israel has also long braced itself for a reprisal attack by Hezbollah for the explosion in Damascus in 2008 which killed Imad Mughniyeh, one of its top military operatives. Israel has never admitted involvement in the assassination.

Washington strongly condemned the attack. The White House press secretary, Jay Carney, said President Barack Obama's "thoughts and prayers are with the families of those killed and injured."

Associated Press reported that in Sofia, the Bulgarian capital, which is 250 miles west of the resort where the blast happened, the mayor Yordanka Fandakova had ordered a stronger police presence at all public places frequented by its Jewish community.